1. Technical Field
The present invention relates to an inertial sensor.
2. Description of the Related Art
Recently, an inertial sensor has been used in various applications, for example, military such as an artificial satellite, a missile, an unmanned aircraft, or the like, vehicles such as an air bag, electronic stability control (ESC), a black box for a vehicle, or the like, hand shaking prevention of a camcorder, motion sensing of a mobile phone or a game machine, navigation, or the like.
The inertial sensor generally adopts a configuration in which a mass body is adhered to an elastic substrate such as a membrane, or the like, in order to measure acceleration and angular velocity. Through the above-mentioned configuration, the inertial sensor may calculate the acceleration by measuring inertial force applied to the mass body and may calculate the angular velocity by measuring Coriolis force applied to the mass body.
In detail, a scheme of measuring the acceleration and the angular velocity using the inertial sensor is as follows. First, the acceleration may be calculated by Newton's law of motion “F=ma”, where “F” represents inertial force applied to the mass body, “m” represents a mass of the mass body, and “a” is acceleration to be measured. Among others, the acceleration a may be obtained by sensing the inertial force F applied to the mass body and dividing the sensed inertial force F by the mass m of the mass body that is a predetermined value. Further, the angular velocity may be obtained by Coriolis force “F=2mΩ×v”, where “F” represents the Coriolis force applied to the mass body, “m” represents the mass of the mass body, “Ω” represents the angular velocity to be measured, and “v” represents the motion velocity of the mass body. Among others, since the motion velocity V of the mass body and the mass m of the mass body are values known in advance, the angular velocity Ω may be obtained by detecting the Coriolis force (F) applied to the mass body.
Meanwhile, the inertial sensor according to the prior art includes a piezoelectric material disposed on a membrane (a diaphragm) in order to sense driving a mass body or displacement of the mass body, as disclosed in Patent Document of the following Prior Art Document. In this configuration, in order to measure angular velocity (Ω) in a three-axis (X, Y, and Z axes) direction, the mass body should vibrate in at least two-axis (for example, X and Z axes) direction. Therefore, in the inertial sensor according to the prior art, the mass body is vibrated in the X direction, forcibly stopped, and then vibrated in the Z axis direction, through time division. However, in the inertial sensor according to the prior art, when the mass body is forcibly stopped and then vibrated in the Z axis, crosstalk is generated in the X axis, such that it is difficult to accurately measure the angular velocity (Ω).
In order to solve this problem, a method of measuring angular velocity (Ω) by including two inertial sensors, that is, one inertial sensor vibrating a mass body in an X axis direction and the other inertial sensor vibrating the mass body in a Z axis direction may be considered. However, in the case in which two inertial sensors are included, a manufacturing process is complicated, and a manufacturing cost is excessively increased.